The underfloor air-conditioning system is a system for performing indoor air conditioning, with an underfloor chamber formed between a floor slab and a floor panel, by feeding conditioned air from an air conditioner to the underfloor chamber and by discharging the conditioned air through an outlet or outlets provided in the floor panel.
FIG. 16 shows an example of conventional air discharge units to be used in such an underfloor air-conditioning system. This air discharge unit is disclosed in Japanese Utility Model Laid-Open Publication SHO 63-196043. In this unit, a cylindrical duct D is provided below an outlet O which opens in a floor panel A, with a lower-end opening of the cylindrical duct confronting a floor slab S. A discharge grille G enabled to adjust the angle of the discharged air stream is provided at an upper end of the duct D, while an axial fan FP constituted of a propeller fan driven by a motor M is provided inside the duct D. This fan FP makes up for the force with which the conditioned air is fed under pressure from an air conditioner (not shown) side to an underfloor chamber J provided below the floor panel A, so that the conditioned air can be smoothly fed to the indoor side.
However, the air discharge unit using the axial fan FP, in which the air is allowed to flow in an axial direction of the fan, tends to increase the heightwise thickness of the whole unit. Also, because the axial fan FP sucks air through the opening provided at the lower end of the duct D, there is a need for providing a space of a certain height below the duct D to introduce the air. This results in a problem since the air discharge unit using the axial fan FP needs a large installation space in the axial direction therefore, it is difficult to install in a limited narrow underfloor space. Another problem is that the unit involves noise having components of high frequencies, thus being harsh.
FIG. 17 shows an air discharge unit as disclosed in Japanese Patent Laid-Open Publication HEI 7-91730, which is particularly intended to thin the heightwise thickness of the unit. In FIG. 17, components similar to those shown in FIG. 16 are designated by the same reference symbols. In the air discharge unit shown in FIG. 17, a pair of crossflow fans FC, FC are placed in a confronting manner on opposite sides of a discharge grille G, so that air taken in sideways is bent upward by a partitioning plate P so as to reach the discharge grille G.
However, this air discharge unit using a pair of crossflow fans FC, FC, in which the air flow taken in sideways is forcedly bent upward by the partitioning plate P, is large in pressure loss. Moreover, although the unit can be thinned heightwise, the unit would be enlarged horizontally laterally. Therefore, there still exists a problem of poor installability.
As another example of the fan, centrifugal fans such as turbo fans or sirocco fans may be used. However, because this type of fan blows off air radially, it is necessary to form a flow path through which the radially blown air is lead toward the axial direction. This would cause the air discharge unit to be increased in size. This would also cause the pressure loss within the system to be increased, so that noise produced would be as big as, for example, 40-45 dB(A). To reduce this noise, it would be necessary to provide an array of air chambers of specified capacity, in which case the unit could not be downsized.
FIG. 18 shows still another example of the prior art, which is disclosed in Japanese Patent Laid-Open Publication HEI 5-106595. In this prior art, in order to attain a uniform room temperature distribution, air to be discharged from the outlet is formed into a rotational flow such that an air flow characteristic of good mixability with ambient room air is imparted to the discharged air. For this purpose, a discharge grille GS is provided with a multiplicity of slanted blades K intended to produce a rotational flow by forcedly bending the discharged air circumferentially as well as concentric slits L. The discharge grille GS is fitted to the outlet.
The discharge grille GS shown in FIG. 18 provides an advantage in that the room temperature distribution can be improved by the rotational flow, which in turn allows the cold draft to be reduced. However, due to the forced change of the direction of the discharged air, there are problems of a large pressure loss and increased noise.
There are known other means to positively reduce the cold draft, as shown in Japanese Patent Laid-Open Publication HEI 7-145985, in which a heater is disposed below the discharge grille so that the temperature of the discharged air is raised. This, however, is not an energy-saving method.